1. Technical Field
The present invention relates to orthopedic surgery and in particular to devices for stabilizing and fixing the bones and joints of the body. Particularly, the present invention relates to a manually operated device capable of reducing a rod into position in a rod receiving notch in the head of a bone screw with a controlled, measured action.
2. Background Art
The spinal column is a complex system of bones and connective tissues that provides support for the human body and protection for the spinal cord and nerves. The human spine is comprised of thirty-three vertebrae at birth and twenty-four as a mature adult. Between each pair of vertebrae is an intervertebral disc, which maintains the space between adjacent vertebrae and acts as a cushion under compressive, bending and rotational loads and motions.
There are various disorders, diseases and types of injury, which the spinal column may experience in a lifetime. The problems may include but are not limited to scoliosis, kyphosis, excessive lordosis, spondylolisthesis, slipped or ruptured disc, degenerative disc disease, vertebral body fracture, and tumors. Persons suffering from any of the above conditions typically experience extreme or debilitating pain and often times diminished nerve function.
One of the more common solutions to any of the above mentioned conditions involves a surgical procedure known as spinal fusion. A spinal fusion procedure involves fusing two or more vertebral bodies in order to eliminate motion at the intervertebral disc or joint. To achieve this, natural or artificial bone, along with a spacing device, replaces part or all of the intervertebral disc to form a rigid column of bone, which is stabilized by mechanical hardware.
The mechanical hardware used to immobilize the spinal column typically involves a series of bone screws and metal rods or plates. When the spine surgery is performed posteriorly, it is common practice to place bone screws into the vertebral bodies and then connect a metal rod between adjacent vertebral bodies. When the spine surgery is performed anteriorly, it is common practice to attach a thin metal plate directly to the vertebral bodies and secure it to each vertebral level using one or more bone screws.
The process of properly inserting the spinal rod into the receiving slot of a bone screw and then securing that connecting rod in place often can require that the surgeon use a number of instruments and expend a great deal of time and effort to accomplish the task. When bone screws in several adjacent vertebrae are to be securely connected by a spinal rod, the repeated process of inserting the rod into the heads of the bone screws and then securing the rod in place for each respective bone screw can be difficult, tiresome and time consuming. Further, the alignment of the rod as it connects to each of the sequential bone screws may require adjustment during the procedure and, therefore it is necessary that a device and method be provided by which the rod can be reduced into the head of each of the sequentially aligned bone screws and, as necessary, easily adjusted so as to facilitate the process for the surgeon with minimal effort and loss of time.
Conventional efforts to meet this need have fallen short in that no instrument has as yet been provided that effectively reduces in a controlled, measured way a connecting rod into position in the receiving slot of the head of a bone screw and holds that rod in position while other portions of the connecting rod are positioned and reduced into other bone screws allowing for position adjustment as necessary during the process.
For these reasons there remains a need for a device that is capable of securely grasping the head of a bone screw in a controlled, measured manner and reducing a posteriorly introduced rod into the head of that bone screw in such a way as to permit easy position adjustment as other portions of the rod are reduced into other bone screws.